Striped tr excluding subtable

I have a table (Maintable) with information and inside the table. Furthermore, each tr has a sub-table with further information that can be collapsed if needed. Now, i want the tr's in the maintable to be striped. I tried out to use:

tr:nth-child(even)

Unfortunately, also the tr's from the subtable are counting for the even and odd. Therefore, it is not working.

So my question is, whether and how it is possible just to use the "Maintable" and stripe these rows.